In a radio network system, operability is maintained by performing various tests on the network elements. Naturally one of the most critical objects for testing is a base transceiver station (BTS) realizing the radio link towards a mobile terminal. Although testing is of utmost importance, likewise it is important that the performed tests do not disturb the normal operation and traffic carried out by the base station.
One type of functionality test is a so-called loop-test, where a signal portion is transported from the transmission equipment to the receiving equipment in a base station. In one prior art solution, U.S. Pat. No. 5,572,510, relating to the GSM (Global System for Mobile Communication) radio system, the transmission and receiving frequencies in the loop-test are situated a frequency division duplex (FDD) apart from each other.
In the prior art solutions, functionality tests, such as the loop test, have been performed during low traffic time in order to ensure the availability of resources. In the GSM system, the measurements are limited to idle time slots in the channel structure. The need for resources is emphasized by the fact that when performing a test, corresponding resources are needed in the uplink and in the downlink. In the GSM system, corresponding resources mean that the uplink and downlink resources are separated from each other by three timeslots. Therefore tests can in practice only last a few milliseconds at a time and continuous testing, for instance, is not possible.